The FBI did not want to disrupt the campaign, so after receiving evidence of suspicious contacts, they opted for sending an informant instead, the New York Times newspaper reported on Saturday, citing unnamed law enforcement officials.
The informant, who is reportedly a US professor teaching in the United Kingdom, contacted several members of the campaign, including former aides Carter Page and George Papadopoulos, as well as former Trump's National Security Adviser Michael Flynn.
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US law enforcement is leading a special counsel investigation of alleged Russian interference in the 2016 US presidential election and purported ties between Moscow and Trump's campaign. Both Russian officials and the US president have denied the allegations.
